Exemplary embodiments of the present invention relate to pressurized-gas containers, and, more specifically, exemplary embodiments of the present invention relate to filling pressurized-gas containers with gas.
Air bag modules or inflatable cushions have become common in modern automobiles for protecting vehicle occupants during collisions. An air bag module typically comprises at least an inflatable cushion and an inflator housing a highly pressurized gas for inflating the cushion. When a vehicle undergoes a collision, a sensor detects the rapid change in motion and provides an electrical signal to activate or ignite an inflator. When ignited, the inflator releases the stored pressurized gas into the cushion, which expands from a folded position to deploy into the vehicle.
One particular type of inflator is a heated gas inflator, in which an ignitable mixture of gases is stored under pressure. The ignitable mixture of gases in such an inflator generally includes hydrogen and/or a hydrogen-hydrocarbon mixture (for example, a hydrogen-propane mixture), and an inert gas or premixed inert gas mixture. A heated gas inflator includes a gas storage chamber or an enclosure for holding the ignitable gas mixture under pressure. An inflator will generally also include an initiator or squib separated from an interior of the inflator by a membrane or a burst disk that the initiator or squib ruptures upon activation to be in fluid communication with the ignitable gas mixture. During operation, the ignitable gas is ignited by the initiator or squib to heat the inert gas or gas mixture, thereby providing an expanding gas and increasing the pressure within the enclosure. The increased pressure causes the burst disk to rupture, thereby enabling the pressurized gases to exit from the inflator output and ultimately inflate the inflatable cushion.
During manufacture of the inflator, the gases are provided to the enclosure under pressure through a small “fill aperture” in an end of the enclosure. After the gases have been placed within the enclosure, a welding process is used to permanently seal the fill aperture. Due to the ignitable nature of the gases used, however, the current fill process requires that the fill aperture first be temporarily sealed to prevent the ignitable gas mixture from escaping from the enclosure and inadvertently igniting as a result of heat generated by the welding process that is used to provide a more permanent closure of the fill aperture.
To provide for both the temporary seal and the more permanent closure weld to be performed, the fill aperture is constructed to have a multi-surface machined interface. In a typical instance, the fill aperture is be formed with multiple stepped aperture portions including a narrower first aperture portion defined by an inner side-wall surface for allowing the sealing member to be inserted and guided therein to form the temporary seal, a second aperture portion defined by an inner-side wall surface and a step surface for distancing the temporary seal from the closure weld, and a wider third aperture portion defined by an inner-side wall surface and a step surface for defining an edge to allow a clean welding location for the closure weld.
The multi-surface machined interface of the fill aperture, in turn, requires that the sealing member be formed as a multi-machined member with a sealing portion for forming the temporary seal and a head portion for forming the closure weld. It should be appreciated that the manufacture of corresponding multi-machined sealing members and fill apertures is complex and expensive, and the aforementioned process of sealing an inflator is also complex. In addition to this complexity, numerous other drawbacks exist in the current inflator manufacture process. For example, the sealing portion of a sealing member may shift out of position within the fill aperture or may not always properly align within the fill aperture, which can result in combustible gas leaking from the inflator and being inadvertently ignited.
Accordingly, it is desirable to provide for the manufacture of pressurized inflators in a more easy, effective, and efficient manner.